The present invention generally relates to ground anchors. More specifically, the present invention relates to systems for driving ground anchors through the ground with a drive rod or drive gad.
A ground anchor is a device which is driven down into soil for securing an anchor rod or cable thereto. The anchor rod or cable has a portion which extends above the surface of the ground which can then be used for anchoring an object. A ground anchor has a socket which has been traditionally configured to loosely receive a drive gad which aligns the anchor in a driving position, so that a cutting edge of the anchor leads a direction of anchor travel.
In prior art systems, the drive gad transmits impacting blows to the anchor, pounding it through the soil with an incremental downward movement. When the anchor has been pounded to a desired depth, the drive gad is pulled away, out of the socket. The anchor rod (or cable) is pivotally attached to the anchor. The anchor rod is pulled through the ground with the anchor via the pivotal connection as the anchor is pounded into the ground. Therefore, the pivotal connection absorbs the momentum of the anchor rod after each impact.
When a desired depth has been reached, the drive gad is removed from the anchor. An upward force on the anchor rod causes the anchor to re-align into an anchoring orientation in the ground so that the anchor cannot be pulled out. Such a ground anchor is disclosed in U.S. Pat. No. 4,802,317, which is incorporated herein by reference.
Prior art driving systems utilize an impact device, such as a jackhammer, to pound the anchor through the ground with a unidirectional force. For example, such driving systems are disclosed in U.S. Pat. Nos. 4,802,317, 5,029,427, and 5,031,370. In practice, impact driving systems result in undesirable effects.
For instance, an impact driving system generates repeated unidirectional blows through a drive gad, resulting in damage and high wear to the anchor and to the drive gad. Particularly, high wear occurs at the pivotal connection of the anchor rod to the anchor, due to repeated absorbing of anchor rod momentum after impact. An anchor rod can weigh as much as twenty or thirty pounds, thus having significant momentum to be absorbed by a typical pin-type pivotal connection. Also, high wear occurs at the point of impact between the drive gad and the socket of the anchor.
A further problem is that impacting generates a great amount of heat and vibration within the drive gad. Heat makes a drive gad difficult to handle when disconnecting it from the actuator, when removing the drive gad from the ground or when attaching a new section thereto. The drive gad can become so hot that it can burn a worker's hand.
Additionally, high grade materials have traditionally been necessary for drive gads due to the effects of unidirectional impact driving. For instance, the materials used to make a traditional drive gad must be very stiff to prevent bending and deflection of the drive gad. If an anchor path is not straight through the ground during impact driving, the drive gad turns in a bowed path. Impact energy is largely wasted from energy transmission into the ground along a bowed drive gad. This slows the driving process and can result in failure of the drive gad.
Moreover, welded joints between multiple drive gad sections are impractical with impact driving. Such joints are desirable because they are simple, however, welded joints quickly fail under impact force conditions. Thus, more expensive mechanical couplings between drive gad sections have previously been necessary such as those disclosed in U.S. Pat. No. 5,031,370.
Therefore, a need exits for an improved ground anchor driving system which overcomes the shortcomings of a traditional unidirectional impact driving system.